How to Grow a Gardenia Tree

Gardenia thunbergia, also called white gardenia and star gardenia, is a flowering, evergreen shrub in U.S. Department of Agriculture plant hardiness zones 10 through 12. Outside of its rather narrow hardiness zone, this shrub does well as a container plant. Gardenias are tropical plants and prefer rich soils in areas with high humidity. Gardenia trees are very fragrant plants and should be planted where they can reach their full height, preferably near a window where the heavy scent can waft indoors.

Things You'll Need

• Compost
• Mulch
• Acid-forming fertilizer

Instructions

1. Amend the planting site with organic compost to ensure good drainage and adequate nutrients. Garden soil will have to be tested prior to planting to ensure proper acidity. Gardenias prefer a pH between 5.0 and 6.5, according to the University of Florida IFAS Extension. Avoid planting this gardenia next to concrete, house foundations or swimming pools, where the soil will most likely be alkaline and will cause problems for the gardenia.

2. Dig a hole for the young plant that is twice the diameter of the root ball and just as deep. Position the root ball so it sits just slightly higher than the soil surface. Water in the backfill once the hole is about half full with soil. This will remove air pockets and ensure that the plant doesn't sink later.

3. Build a watering ring or dam 2 or 3 inches tall around the base of the young tree to help retain water. Water the young gardenia twice a week during the first six weeks after planting.

4. Mulch gardenia shrubs with 2 to 3 inches of organic mulch to avoid wide variations in soil moisture. Fluctuations in moisture and temperature could cause the buds to drop and the leaf tips to blacken.

5. Water the established gardenia moderately and regularly, but do not overwater. Check the soil before each watering. If it is wet, wait another day or two and check again.

6. Maintain soil acidity. If the soil loses acidity, the plant may yellow. According to the University of Florida IFAS Extension, two or three applications per year of an "acid-forming" fertilizer will keep the soil acidic enough to support growth.

7. Prune to shape after flowering.

Container Culture

1. Place a potted gardenia where it will receive bright light. Keep it out of the way of cold drafts from doors and windows, especially during winter. If placed outside, choose a location in light shade that provides protection from hot afternoon sun.

2. Maintain humidity. Indoors, this is accomplished by placing the pot in a pebble tray filled with water. In winter conditions, it may help to mist the foliage with a spray bottle.

3. Apply iron supplements in the form of foliar sprays. This particular gardenia is susceptible to iron deficiency.

Tips & Warnings

• Select a nematode-resistant gardenia grafted onto Gardenia jasminoides rootstock.

• This particular gardenia's preference for acidic soil, coupled with the difficulty of permanently altering soil pH to support such acidity, makes container culture especially suitable for Gardenia thunbergia.

• A healthy container-grown gardenia will reach a height of 6 to 8 feet at maturity. Planted outdoors and maintained as a tree, a gardenia may grow 15 feet tall.

• Gardenias are not salt-tolerant.

References

• North Country Times: Get the Most Fragrance from Your Gardenias
• Missouri Botanical Garden: Gardenia thunbergia
• University of Florida IFAS Extension: Gardenia thunbergia
• University of Florida IFAS Extension: Growing Gardenias in Florida